Optical disc recording apparatus recording method, and a storage medium for storing optical disc recording program for facilitating dubbing an audio stream

ABSTRACT

A recordable optical disc stores one or more video objects. A video stream, a first audio stream, and a second audio stream which is used for dubbing are multiplexed into each video object. Also, an optical disc recording apparatus generates the second audio stream by an audio stream generating device, and multiplexes the generated second audio stream into each video object together with the video object and the first audio stream by a multiplexor. The generated video objects are recorded onto the recordable optical disc by a recording device. The optical disc in which such video objects are stored facilitates dubbing.

This is a Rule 1.53(b) Divisional application of Ser. No. 09/210,948,filed Dec. 15, 1998.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention generally relates to a rewriteable optical disc, anoptical disc recording apparatus, an optical disc recording method, anda storage medium for storing optical disc recording program, andspecifically to a rewriteable optical disc, an optical disc recordingapparatus, and an optical disc recording method for facilitatingdubbing, and a storage medium for storing an optical disc recordingprogram for facilitating dubbing.

(2) Description of the Prior Art

Recently, DVD(Digital Video/Versatile Disc)-RAM, one of rewriteableoptical discs, has been commercialized. The DVD-RAM is aphase-change-type disc having a capacity of several giga bytes. Now thatMPEG and MPEG2, standards for compressing/encoding AV (Audio Visual)data, have gone into practical use, it is expected that the DVD-RAM willbe used not only in computers but as an AV recording/reproducing medium.That is, the widespread expectation is that the DVD-RAM will beprevalent and replace the magnetic tape which has been a major AVrecording/reproducing medium.

It is possible for users to record data onto DVD-RAMs while this is notpossible with read-only DVDs (hereinafter referred to as DVD-ROMs). As aresult, it is expected that DVD-RAMs provide a wide range of uses.

However, it is not so easy to perform dubbing on conventional opticaldiscs as on the magnetic tapes.

The magnetic tapes have independent areas for recording video tracks andaudio tracks. Also, video data and audio data are read/written from/ontothe magnetic tapes via respectively independent magnetic heads.Accordingly, it is very easy to perform dubbing of audio data on themagnetic tapes. In case of analog video tape recorders, the time (delay)taken for starting reproducing audio or video data read from themagnetic tape via the head is nearly zero. This is the same for the time(delay) taken for starting writing input audio or video data onto themagnetic tape via the head. As a result, data can be recorded onto themagnetic tape at the same time as the data having been recorded on themagnetic tape is reproduced.

In contrast, in case of an optical disc, the video stream and audiostream are multiplexed into one MPEG stream to be recorded onto thedisc. Also, only one pickup is used for both reading and writing datafrom/onto the optical disc. In the MPEG stream, the video stream isplaced before and is processed earlier than the audio stream. This isbecause the amount of video data to be decoded is greater than that ofaudio data. Such data structure of the MPEG stream and the constructionof the recording/reproducing apparatus make it difficult to performdubbing to record dubbed data onto the optical disc.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an opticaldisc which allows the dubbing to be performed as easily as magnetic tapemedium, and an optical disc recording apparatus, an optical discreproducing apparatus, and a program storage medium storing a programexecuted in the optical disc recording apparatus.

The above object is fulfilled by a recordable optical disc comprising: adata area in which one or more video objects are recorded, where a videostream, a first audio stream, and a second audio stream are multiplexedinto the one or more video objects, the second audio stream being usedfor dubbing.

With the above-stated construction, it is possible to perform dubbingeasily since the second audio stream for dubbing is recorded beforehandin the video objects. It is also possible to record the dubbing audiodata together with the original audio data (the first audio stream)since the first and second audio streams are separately recorded.

As a result, it is possible to achieve new applications (e.g.,applications for practicing pronunciation of some language andapplications including dubbings for Karaoke) which have not beenachieved conventionally in recordable optical discs. It is also possibleto repeatedly record the dubbing while maintaining the original audiodata.

In the above recordable optical disc, the second audio stream fordubbing may have the same reproduction time period as that of the firstaudio stream.

With such a construction, it is possible to ensure that the first audiostream is dubbed onto the second audio stream over the entirereproduction period.

In the above recordable optical disc, the second audio stream fordubbing may be recorded with the same bit rate as the first audiostream.

With such a construction, it is possible to ensure that the second audiostream for dubbing has the same audio quality as the first audio stream.This is achieved, for example, by using the same encoding mode and thesame sampling frequency for the second audio stream as the first audiostream.

In the above recordable optical disc, the second audio stream fordubbing may include audio data which has been generated from the samesource as the first audio stream.

With such a construction, the second audio stream for dubbing has thesame source as the first audio stream. This enables the audio stream tobe used for the performance of a partial dubbing. Furthermore, thesecond audio stream having had partial dubbing performed dubbingincludes the same audio data as the first audio stream in a part otherthan the part in which the dubbing data is recorded. Therefore, thereproducing apparatus needs not switch between the first and secondaudio streams during the reproduction.

In the above recordable optical disc, the first audio stream may includea plurality of packs which each have a predetermined size, and thesecond audio stream may include a plurality of packs respectivelycorresponding to the plurality of packs included in the first audiostream.

Also, in the above recordable optical disc, each of the plurality ofpacks in the second audio stream may include the same audio data as thatincluded in a corresponding one of the plurality of packs in the firstaudio stream.

With such a construction, the second audio stream for dubbingcorresponds to the first audio stream in units of packs and has the sameaudio data. As a result, in addition to the above-described partialdubbing, it is possible to return the second audio stream to the statebefore dubbing. This is achieved by copying the audio data of packs ofthe first audio stream to the corresponding packs of the second audiostream.

The above recordable optical disc may further comprise: a managementarea for storing one or more pieces of management information whichrespectively correspond to the one or more video objects, each of theone or more pieces of management information shows a state of the secondaudio stream in a corresponding video object and indicates whetherdubbing has been performed on the second audio stream in thecorresponding video object.

With the above construction, it is possible for the recording apparatusand the reproducing apparatus to manage whether the dubbing stream hashad dubbing performed by referring, to the management information.

In the above recordable optical disc, each of the one or more pieces ofmanagement information may further indicate one of a first state, asecond state, and a third state, where the first state indicates thatthe second audio stream includes the same audio data as the first audiostream, the second state indicates that the second audio stream includesaudio data which has been generated from the same source as the firstaudio stream, and the third state indicates that audio data of thesecond audio stream is irrelevant to audio data of the first audiostream.

With such a construction, it is possible for the recording apparatus andthe reproducing apparatus to manage the state of the dubbing stream byreferring to the management information.

The above object is also fulfilled by a recordable optical disccomprising: a data area in which one or more video objects are recorded,where a plurality of elementary streams are multiplexed into the one ormore video objects, where one of the plurality of elementary streams isa video stream and another one is a dubbing stream which is used fordubbing either of audio data and sub-picture data; and a management areafor storing one or more pieces of management information whichrespectively correspond to the one or more video objects, each of theone or more pieces of management information shows a state of thedubbing stream in a corresponding video object.

With the above construction, the dubbing stream is multiplexed into thevideo objects beforehand, and an area is secured in the dubbing streamso that either audio data or sub-picture data is recorded in the area.This facilitates the dubbing. Furthermore, it is possible for therecording apparatus and the reproducing apparatus to manage whether thedubbing stream has had dubbing performed by referring to the managementinformation.

In the above recordable optical disc, the dubbing stream may be used fordubbing the sub-picture data representing one or more still pictures,each of the one or more video objects includes a plurality of videoobject units, and each of the plurality of video object units includes apart of the video stream corresponding to a predetermined reproductiontime period and includes a part of the dubbing stream which is to bereproduced together with the part of the video stream, where the part ofthe dubbing stream corresponds to at least one still picture, and eachof the one or more pieces of management information indicates whetherdubbing has been performed on the dubbing stream in the correspondingvideo object.

Also, in the above recordable optical disc, the part of the dubbingstream included in each video object unit may correspond to a stillpicture having a predetermined size.

With the above construction, it is possible to easily dub at least onestill picture into each video object unit.

The above object is also fulfilled by an optical disc recordingapparatus for recording one or more video objects onto an optical disc,where each of the one or more video objects include a video stream, afirst audio stream and a second audio stream, the optical disc recordingapparatus comprising: an input unit for receiving the video stream andthe first audio stream; an audio stream generating unit for generating,based on the received first audio stream, a second audio stream which isused for dubbing; a multiplexing unit for generating the one or morevideo objects by multiplexing the generated second audio stream, thereceived video stream, and the received first audio stream into the oneor more video objects; and a recording unit for recording the generatedone or more video objects onto the optical disc.

With the above construction, the second audio stream for dubbing ismultiplexed into the video objects beforehand during the first recordingonto the optical disc. As a result, it is possible to generate anoptical disc in which video objects; facilitating the dubbing arerecorded beforehand. It is also possible to record the dubbing audiodata together with the original audio data (the first audio stream)since the first and second audio streams are separately recorded.

In the above optical disc recording apparatus, the first audio streamreceived by the input unit may include packs which each have a fixedsize, and the audio stream generating unit includes: a buffer forsequentially storing packs included in the received first audio stream;and a control unit for performing a control so that the packs stored inthe buffer are output to be included in the second audio stream.

Also, in the above optical disc recording apparatus, each pack mayinclude a time stamp and a stream identifier, the time stamp specifyinga time at which each pack is output from a track buffer of a reproducingapparatus, and the control unit updates time stamps and streamidentifiers of the packs stored in the buffer.

With the above construction, it is possible to generate the second audiostream for dubbing by copying each pack of the first audio stream almostas it is. This relieves the optical disc recording apparatus of havingan audio encoder for generating the second audio stream for dubbing.

The above optical disc recording apparatus may further comprise: areading/writing unit for reading a video object from the optical disc; afirst buffer unit including a first reading buffer and a first writingbuffer, the first reading buffer storing a part of the read videoobject, and the first writing buffer storing a part of the read videoobject which is to be written onto the optical disc; a second bufferunit including a second reading buffer and a second writing buffer, the:second reading buffer storing a part of the read video object, and thesecond writing buffer storing a part of the read video object which isto be written onto the optical disc; and a dubbing control unit forperforming a control so that while the video object is either read fromor written onto the optical disc using one of the first buffer unit andthe second buffer unit, the second audio stream in the part of the videoobject stored in the reading buffer of the other one of the first bufferunit and the second buffer unit is updated, and the part of the videoobject including the updated second audio stream is stored in thewriting buffer of the other buffer unit, where the reading/writing unitsequentially writes the part of the video object in the first writingbuffer and the part of the video object in the second writing bufferonto the optical disc, where after the second audio stream has haddubbing performed, the dubbing control unit is capable of restoring thesecond audio stream to a state before the dubbing by copying the audiodata of the first audio stream to the second audio stream.

With the above construction, the dubbing control unit alternatelyswitches the first and second buffer units to read/write the opticaldisc or to perform the dubbing (update the second audio stream). Thisachieves the reproduction and dubbing performed in real time. Also, thesecond audio stream can easily be restored to the original state afterdubbing is performed on the second audio stream.

In the above optical disc recording apparatus, the dubbing control unitmay instruct the reading/writing unit to read a piece of managementinformation corresponding to the video object read by thereading/writing unit, updates the read piece of management informationso that the information indicates that dubbing has been performed on thevideo object, and instructs the reading/writing unit to write theupdated piece of management information onto the optical disc.

With the above construction, it is possible to update the managementinformation so that it indicates that dubbing has been performed on thedubbed video object.

The above object is also fulfilled by an optical disc recordingapparatus for recording one or more video objects onto an optical disc,where each of the one or more video objects includes a video stream, theoptical disc recording apparatus comprising: an input unit for receivingthe video stream; a dubbing stream generating unit for generating adubbing stream which is used for dubbing; a multiplexing unit forgenerating the one or more video objects by multiplexing the generateddubbing stream and the received video stream into the one or more videoobjects; a management information generating unit for generating one ormore pieces of management information which respectively correspond tothe one or more video objects, each of the one or more pieces ofmanagement information indicates whether dubbing has been performed onthe dubbing stream in the corresponding video object; and a recordingunit for recording the generated one or more video objects and thegenerated one or more pieces of management information onto the opticaldisc.

With the above construction, the optical disc recording apparatusmultiplexes the dubbing stream into the video objects beforehand duringthe first recording onto the optical disc. As a result, it is possibleto generate an optical disc in which video objects facilitating thedubbing of audio data or sub-picture data are recorded beforehand.Furthermore, it is possible for the recording apparatus and thereproducing apparatus to manage whether the dubbing stream has haddubbing performed by referring to the management information.

The above object is also fulfilled by a method for recording one or morevideo objects onto an optical disc, the method comprising: an obtainingstep for obtaining a video stream and a first audio stream; an audiostream generating step for generating a second audio stream having a bitrate with which audio data corresponding to a reproduction time periodof the first audio stream is recorded into the second, audio stream; anda recording step for generating the one or more video objects bymultiplexing the generated second audio stream, the obtained videostream, and the obtained first audio stream into the one or more videoobjects and recording the generated one or more video objects onto theoptical disc.

With the above construction, the second audio stream for dubbing ismultiplexed into the video objects beforehand during the first recordingonto the optical disc. As a result, it is possible to generate anoptical disc in which video objects facilitating the dubbing arerecorded beforehand. It is also possible to record the dubbing audiodata together with the original audio data (the first audio stream)since the first and second audio streams are separately recorded.

The above object is also fulfilled by a computer-readable storage mediumstoring a program for recording one or more video objects onto anoptical disc, the program comprising: a program segment for instructinga computer to receive a video stream and a first audio stream; a programsegment for instructing the computer to generate a second audio streamhaving a bit rate with which audio data corresponding to a reproductiontime period of the first audio stream is recorded into the second audiostream; a program segment for instructing the computer to generate theone or more video objects by multiplexing the generated second audiostream, the received video stream, and the received first audio streaminto the one or more video objects; and a program segment forinstructing the computer to record the generated one or more videoobjects onto the optical disc.

With the above construction, a computer executing the program stored inthe storage medium multiplexes the second audio stream for dubbing intothe video objects beforehand during the first recording onto the opticaldisc. As a result,: it is possible to generate an optical disc in whichvideo objects facilitating the dubbing are recorded beforehand. It isalso possible to record the dubbing audio data together with theoriginal audio data (the first audio stream) since the first and secondaudio streams are separately recorded.

In the above computer-readable storage medium, the generated secondaudio stream may have the same audio data as the first audio stream.

Also, in the above computer-readable storage medium, the received firstaudio stream may include packs which each have a fixed size, and theaudio stream generating program segment may instruct the computer totemporarily store packs included in the received first audio stream intoa buffer in sequence, and instruct the computer to perform a control sothat the packs stored in the buffer are output to be included in thesecond audio stream.

Also, in the above computer-readable storage medium, each pack mayinclude a time stamp and a stream identifier, the time stamp specifyinga time at which each pack is output from a track buffer of a reproducingapparatus, and the audio stream generating program segment instructs thecomputer to update time stamps and stream identifiers of the packsstored in the buffer.

With the above construction, it is possible for the computer executingthe program stored in the storage medium to generate the second audiostream for dubbing by copying each pack of the first audio stream almostas it is.

The above computer-readable storage medium may further comprise: aprogram segment for instructing the computer to, after the second audiostream has had dubbing performed, restore the second audio stream to astate before the dubbing by copying the audio data of the first audiostream to the second audio stream.

With such a construction, the second audio stream can easily be restoredto the original state after dubbing is performed on the second audiostream.

The above object is also fulfilled by an optical disc reproducingapparatus for reproducing an optical disc, where the optical discincludes: a data area in which one or more video objects are recorded,where a video stream, a first audio stream, and a second audio streamare multiplexed into the one or more video objects; and a managementarea for storing one or more pieces of management information whichrespectively correspond to the one or more video objects, where thesecond audio stream has a bit rate with which audio data correspondingto a reproduction time period of the first audio stream is recorded intothe second audio stream, where each of the one or more pieces ofmanagement information further indicates one of a first state, a secondstate, a third state, and a fourth state, where the first stateindicates that the second audio stream includes the same audio data asthe first audio stream, the second state indicates that the second audiostream includes audio data which has been generated from the same sourceas the first audio stream, the third state indicates that audio data ofthe second audio stream is irrelevant to audio data of the first audiostream, and the fourth state indicates that the second audio stream hashad dubbing performed, the optical disc reproducing apparatuscomprising: a reading unit for reading a video object and a piece ofmanagement information corresponding to the video object from theoptical disc; a reproducing unit for reproducing the video stream andthe first audio stream included in the read video object; a control unitfor controlling the reproducing unit so that when the piece ofmanagement information indicates the fourth state, the reproducing unitis allowed to change reproductions of the first audio stream and thesecond audio stream in accordance with an instruction to change audiostreams input from a user, and that when the piece of managementinformation indicates either of the first state and the second state,the reproducing unit is not allowed to change reproductions of the firstaudio stream and the second audio stream even when the instruction isinput from the user, and the reproducing unit notifies the user thataudio streams cannot be changed.

With the above construction, the control unit controls the reproducingunit so that when the optical disc has had dubbing performed (thirdstate), the reproducing unit changes reproductions of the first audiostream and the second audio stream in accordance with an instructionfrom a user, and that when the dubbing has not been performed on theoptical disc (first or second state), it notifies the user that audiostreams cannot be changed. That is, the optical disc reproducingapparatus cautions the user that audio streams cannot be changed sincedubbing has not been performed yet. The user is notified so for thefollowing reason. If the first audio stream is changed to the secondaudio stream when the dubbing has not been performed on the optical disc(first or second state), the user may misunderstand the operationthinking that the reproducing apparatus has broken down and failed tochange the audio streams since the user will hear the same sound.

The above object is also fulfilled by an optical disc reproducing methodfor reproducing an optical disc, where the optical disc includes: a dataarea in which one or more video objects are recorded, where a videostream, a first audio stream, and a second audio stream are multiplexedinto the one or more video objects; and a management area for storingone or more pieces of management information which respectivelycorrespond to the one or more video objects, where the second audiostream has a bit rate with which audio data corresponding to areproduction time period of the first audio stream is recorded into thesecond audio stream, where each of the one or more pieces of managementinformation further indicates one of a first state, a second state, athird state, and a fourth state, where the first state indicates thatthe second audio stream includes the same audio data as the first audiostream, the second state indicates that the second audio stream includesaudio data which has been generated from the same source as the firstaudio stream, the third state indicates that audio data of the secondaudio stream is irrelevant to audio data of the first audio stream, andthe fourth state indicates that the second audio stream has had dubbingperformed, the optical disc reproducing method comprising: a readingstep for reading a video object and a piece of management informationcorresponding to the video object from the optical disc; a reproducingstep for reproducing the video stream and the first audio streamincluded in the read video object; a control step for, when the piece ofmanagement information indicates the fourth state, allowing thereproducing step to change reproductions of the first audio stream andthe second audio stream in accordance with an instruction to changeaudio streams input from a user, and that when the piece of managementinformation indicates either of the first state and the second state,not allowing the reproducing step to change reproductions of the firstaudio stream and the second audio stream even when the instruction isinput from the user, and the reproducing step notifies the user thataudio streams cannot be changed.

With the above construction, the optical disc reproducing methodcautions the user that audio streams cannot be changed since dubbing hasnot been performed yet. The user is notified so for the followingreason. If the first audio stream is changed to the second audio streamwhen the dubbing has not been performed on the optical disc (first orsecond state), the user may misunderstand the operation thinking thatthe reproducing apparatus has broken down and failed to change the audiostreams since the user will hear the same sound.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings which illustrate a specificembodiment of the invention. In the drawings:

FIG. 1 shows the appearance and the recording area of a DVD-RAM discwhich is a recordable optical disc described as an embodiment of thepresent invention;

FIG. 2 shows the cross-section and surface of a DVD-RAM cut at theheader of a sector;

FIG. 3A shows the plurality of zone areas provided on a DVD-RAM;

FIG. 3B shows a horizontal arrangement of the lead-in area, the lead-outarea, and the zone area 0-23 that were shown in FIG. 3A;

FIG. 3C shows logical sector numbers (LSNs) in the volume area;

FIG. 3D shows logical block numbers (LBNS) in the volume area;

FIG. 4 shows a hierarchical relation between zone areas, ECC blocks, andsectors;

FIG. 5 shows directories and AV data and non-AV data recorded on aDVD-RAM disc;

FIG. 6A shows VOBs which are recorded as AV data files “Movie1.VOB” and“Movie2.VOB”;

FIG. 6B shows a structure of VOB in which elementary streams aremultiplexed;

FIG. 7 shows boundaries generated in the audio stream #1 when a partialdubbing is performed on the audio stream #1;

FIG. 8 shows a data format of the video pack;

FIG. 9 shows a data format of the audio pack (MPEG audio);

FIG. 10 shows a data format of the audio pack (AC-3);

FIG. 11 shows a data format of the audio pack (linear PCM);.

FIG. 12 hierarchically shows the data structure of the AV datamanagement file;

FIG. 13 shows relation between “Cell Start Time,” “Cell Playback Time,”“Cell Start Address,” “Cell End Address,” “VOB Start Address,” “VOB EndAddress,” and VOBs;

FIG. 14 shows a relationship between several pieces of informationindicated by respective values of the “Application Flag” of the “Audio1Attribute” in a VOBI;

FIG. 15 shows the construction of an example system using the opticaldisc recording/reproducing apparatus of the present embodiment;

FIG. 16 is a block diagram showing the construction of the DVD recorder10;

FIG. 17 shows a remote controller;

FIG. 18 is a block diagram showing the construction of the MPEG decoder4 shown in FIG. 16;

FIG. 19 is a block diagram showing the construction of the MPEG encoder2 shown in FIG. 16;

FIG. 20 shows the operation executed during the dubbing process;

FIG. 21 shows the construction of the disc access unit 3;

FIG. 22 is a flowchart showing the process of generating packs of thevideo stream and the audio stream #0 which is performed by the systemencoder 2 e;

FIG. 23 is a flowchart showing the process of generating audio packs ofthe audio stream #1 for dubbing;

FIG. 24 is a flowchart of the multiplexing process in which, the systemencoder 2 e multiplexes the video stream and the audio streams #0 and #1in units of packs;

FIG. 25 shows the VOBs output from the system encoder 2 e;

FIG. 26 shows the simulation of the video decoder buffer;

FIG. 27 shows the dubbing process with the timing when the disc accessunit 3 performs reading/writing, and with the timing when the MPEGencoder 2 rewrites the audio stream #1;

FIG. 28 shows a VOB which is read and written during the time periodsshown in FIG. 27;

FIG. 29 shows the control of the switches 3 d and 3 e shown in FIG. 21performed by the control unit 1 with the timing shown in FIG. 27;

FIG. 30 shows the construction of the MPEG encoder which includes twopairs of an audio encoder and an audio buffer;

FIG. 31 shows a structure of the VOB in the second embodiment in whichelementary streams are multiplexed;

FIG. 32 shows a data format of the sub-picture pack;

FIG. 33 hierarchically shows the data structure of the AV datamanagement file;

FIG. 34 is a block diagram showing the construction of the MPEG encoder12; and

FIG. 35 is a block diagram showing the construction of the MPEG decoder14.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

<First Embodiment>

<1 Construction of Optical Disc>

<1-1 Physical Structure of Recordable Optical Disc>

FIG. 1 shows the appearance and the recording area of a DVD-RAM discwhich is a recordable optical disc described as an embodiment of thepresent invention. As shown in the figure, the DVD-RAM disc has alead-in area at its innermost periphery and a lead-out area at itsoutermost periphery, with the data area in between.

The lead-in area records the necessary reference signals for thestabilization of a servo of a recording/reproducing apparatus and alsorecords identification signals used to prevent confusion with othermedia.

The lead-out area records the same type of reference signals as thelead-in area.

The data area, meanwhile, is divided into sectors which are the smallestunit by which the DVD-RAM can be accessed. Here, the size of each sectoris set at 2 KB. The data recorded in the data area includes file systemmanagement information, AV data, AV data management file, and non-AVdata.

The file system management information includes a directory structure ofthe DVD-RAM disc, positions of the recorded files, and information ofthe state of data area assignment. The file system managementinformation is used when files are created, written, read, or deleted.

The AV data is recorded in units of files which respectively correspondto Video OBjects (VOBs). Each VOB is recorded into the disc by anoptical disc recording apparatus in one consecutive recording. Thecontents of the VOBs are, for example, a whole or a part of a movie, ora whole or a part of a TV program.

The non-AV data is data other than AV data and is recorded in units offiles.

FIG. 2 shows the cross-section and surface of a DVD-RAM cut at theheader of a sector. As shown in the figure, each sector is composed of apit sequence that is formed in the surface of a reflective film, such asa metal film, and an uneven part.

The pit sequence is composed of 0.4 μm˜1.87 μm pits that are carved intothe surface of the DVD-RAM to show the sector address.

The uneven part is composed of a concave part called a “groove” and aconvex part called a “land”. Each groove and land has a recording markcomposed of a matal film capable of phase change attached to itssurface. Here, the expression “capable of phase change” means that therecording mark can be in a crystalline state or a non-crystalline statedepending on whether the metal film has been exposed to a light beam.Using this phase change characteristic, data can be recorded into thisuneven part. While it is only possible to record data onto the land partof an MO (Magnetic-Optical) disc, data can be recorded onto both theland and the groove parts of a DVD-RAM, meaning that the recordingdensity of a DVD-RAM exceeds that of an MO disc.

Error correction process is performed for each group of 16 sectors. Inthe present embodiment, each group of 16 sectors that is given an ECC(Error Correcting Code) is called an ECC block.

On a DVD-RAM, the data area is divided into a plurality of zone areas sothat recording/reproducing apparatuses can realize rotation controlcalled Z-CLV (Zone-Constant Linear Velocity) during recording andreproduction.

FIG. 3A shows the plurality of zone areas provided on a DVD-RAM.

As shown in the figure, a DVD-RAM is divided into 24 zone areas numberedzone 0 to zone 23. Each zone area is a group of tracks that are accessedusing the same angular velocity. In this embodiment, each zone areacontains 1888 tracks. The rotational angular velocity of the DVD-RAM isset separately for each zone area, with this velocity being higher thecloser a zone area is located to the inner periphery of the disc. Thisensures that the optical pickup can move at a constant velocity whileperforming access within a single zone area. By doing so, the recordingdensity of DVD-RAM is raised, and rotation control is made easier duringrecording and reproduction.

FIG. 3B shows a horizontal arrangement of the lead-in area, the lead-outarea, and the zone area 0-23 that were shown in FIG. 3A.

The lead-in area and lead-out area each have a DMA (Defect ManagementArea) inside. The DMA records: position information showing thepositions of sectors found to include defects; and replacement positioninformation showing the positions of the sectors replacing the defectivesectors located in a replacement area.

Each zone area has a user area on the inside, and the replacement areaand an unused area are provided at the boundary between zone areas. Theuser area is an area that can be used by the file system as a recordingarea. The replacement area is used to replace defective sectors whensuch defective sectors are found. The unused area is an area that is notused for recording data. Only about two tracks are assigned as theunused area, with such unused area being provided to prevent mistakenidentification of sector addresses. This is because while sectoraddresses are recorded at a same position in adjacent tracks within thesame zone, for Z-CLV the sector addresses are recorded at differentpositions in adjacent tracks at the zone boundary.

In this way, sectors which are not used for data recording exist at theboundaries between zone areas. Therefore, on a DVD-RAM, logical sectornumbers (LSN: Logical Sector Number) are assigned to physical sectors ofthe user area in order starting from the inner periphery toconsecutively show only the sectors used for recording data.

As shown in FIG. 3C, the area that records user data and is composed ofsectors that have been assigned LSNs is called volume area.

Also, as shown in FIG. 3D, in the innermost and outermost peripheries ofthe volume area, volume structure information is recorded to be used todeal with the disc as a logical volume. The rest of the volume areaexcept the areas for recording the volume structure information iscalled partition area. The partition area records files. The logicalblock numbers (LBN: Logical Block Number) are assigned to sectors of thepartition area in order starting from the first sector. Hereinafter, thelogical block number is also called sector address.

FIG. 4 shows a hierarchical relation between zone areas, ECC blocks, andsectors. As shown in the drawing, each zone area includes a plurality ofECC blocks. It is desirable for recording apparatuses that in theoptical discs, areas in units of sectors are assigned to non-AV data,while areas in units of consecutive recording areas are assigned to AVdata so that each consecutive recording area secures uninterruptedreproduction of the AV data. Here, each consecutive recording area iscomposed of consecutive sectors in units of ECC blocks (in other words,each area is an integral multiple of an ECC block) and has apredetermined size (about 7 MB) or more, each consecutive recording areanot outstepping the boundary between zones. However, when the AV dataincludes a plurality of extents, the last extent may be smaller than thepredetermined size. The reason why it is defined that each consecutiverecording area does not outstep the boundary between zones is that anoutstepping of the boundary will change the rotation angular velocity ofthe optical disc, which will disturb the uninterrupted reproduction. Thereason why each consecutive recording area is an integral multiple of anECC block is that the ECC block is the minimum unit dealt with in theECC process.

<1-2 AV File (VOB) and AV Data Management File>

FIG. 5 shows directories and AV data and non-AV data recorded on aDVD-RAM disc.

In the drawing, ellipses represent directories and rectangles representfiles.

The directory “ROOT” includes a directory “RTRW” and two non-AV datafiles: “File1.DAT” and “File2.DAT.” The directory “RTRW” includes an AVdata management file “RTRW.IFO” and a plurality of AV data files:“Movie1.VOB,” “Movie2.VOB,” . . . . Each AV file represents one VOB. TheAV data management file is a file for recording information used formanaging AV files recorded in the current directory (“RTRW”) or on theoptical disc.

<1-2-1 Data Structure of VOB>

As shown in FIG. 6A, the AV data files “Movie1.VOB,” “Movie2.VOB,” . . .are each recorded into the data area as one VOB.

FIG. 6B shows a structure of VOB in which elementary streams (videostreams and audio streams) are multiplexed.

As shown in the drawing, the VOB 70 includes video stream 72, audiostream 73, and audio stream 74. The audio stream 74 is used for dubbing.It is desirable that the audio stream 74, which is dedicated to dubbing,has the same bit rate as the audio stream 73. However, there will be noproblem if the audio stream 74 includes an area in which audio data withthe same time period as the audio stream 73 can be recorded, even if theaudio stream 74 has a different bit rate from the audio stream 73.

The video stream 72 is a compressed data sequence with a variable-lengthbit rate, encoded in compliance with the MPEG2 standard. The videostream 72 includes a plurality of GOPs (Group Of Pictures) which eachinclude a plurality of pictures. For example, as shown in the drawing,the video pictures 71 include compressed/encoded pictures which are anyof I(Intra)-picture, P(Predictive) -picture, and B(Bidirectionallypredictive) -picture defined in MPEG2 standard. Also, as indicated bythe GOP 71 a in FIG. 6B, each GOP includes at least one I-picture and isa video data section corresponding to a reproduction time period ofabout 0.5 seconds. This indicates that independent reproduction in unitsof about 0.5 seconds is possible. It should be noted here that the videopictures 71 in the drawing are shown in the order of decoding, not inthe order of display.

The audio stream (#0) 73 is audio data which should be reproducedsimultaneously with the video stream. In the DVD-RAM, any of three typesof modes: MPEG audio, AC-3, and linear PCM can be used for encodingaudio streams. With the MPEG audio or AC-3, audio data is compressed;with the linear PCM, audio data is not compressed. The audio stream (#0)73 is encoded with any of the three encoding modes.

The audio stream (#1) 74 is an audio stream for dubbing and has the samereproduction time period as the audio stream (#0) 73. It is presumedthat the audio streams #0 and #1 shown in the drawing have the sameencoding mode, the same bit rate, and the same audio data.

VOB 70 is composed of a plurality of Video OBject Units (VOBUs) arrangedin the order of reproduction: VOBU 75 a, VOBU 75 b, VOBU 75 c, . . . .Each VOBU includes video data corresponding to one GOP. Each VOBUincludes packs which respectively belong to the elementary streams. Eachpack has a fixed length (2 KB) andincludes data which is a part of anelementary stream.

The video packs (V_PCK 72 a, V_PCK 72 b, . . .) each include data whichis a part of the video stream 72.

The audio packs (A0_PCK 73 a, A0_PCK 73 b, . . .) each include datawhich is a part of the audio stream 73.

The audio packs (A1_PCK 74 a, A1PCK 74 b, . . . ) each include datawhich is a part of the audio stream 74. In the present embodiment, theaudio stream #1 has the same encoding mode, the same bit rate, and thesame audio data as the audio stream #0 when the audio stream #1 is firstrecorded onto the disc. Therefore, the audio streams #0 and #1 have thesame number 30. of packs.

The audio stream #1 is multiplexed as well as the audio stream #0 tosecure an area in which audio data for dubbing can be recorded.

The above statement is explained more specifically. It is desirable thatthe audio stream (#1) 74 has the same bit rate and the same encodingmode as the audio stream #0. This is because, with the same bit rate andthe same encoding mode, the optical disc recording apparatus cangenerate the audio streams #1 for dubbing without difficulty by copyingthe output of one audio encoder (the audio stream #0). This ensures thatthe audio stream #1 has the same audio quality as the audio stream #0.

Alternatively, the audio stream #1 may have a different bit rate fromthe audio stream #0. In this case, the same audio quality as the audiostream #0 may not be ensured for the audio stream #1. As a result, theoptical disc recording apparatus may include two audio encoders so thatthe audio stream #1 may store the audio data which has the same sourceas that of the audio stream #0.

In any case, the audio stream #1 for dubbing needs to include an area inwhich audio data with the same time period as the audio stream #0 can berecorded. With this arrangement, it is possible to ensure facilitatingdubbing into the audio stream #1 though the audio streams #0 and #1 maybe different in the audio quality due to the difference in the bit rateor the encoding mode.

Furthermore, it is desirable that the audio streams #0 and #1 have thesame audio data content whether they have the same or different encodingmode. The reason for this is as follows. DVD recorders or reproducingapparatuses have one audio decoder. This makes it impossible for such anapparatus to simultaneously reproduce the audio streams #0 and #1. Asshown in FIG. 7, the decoder should be instructed to change thereproduction-target audio streams at the boundaries between the audiostreams #0 and #1 (in both directions) when the audio stream #1 ispartially dubbed. In general, it is difficult to accurately change theaudio streams at the boundaries since a reproduction-target audio streamis specified by a host side, that is, under control of a microcomputer.Under such a condition, it is impossible to ensure uninterruptedreproduction. Accordingly, it is arranged that the audio stream #1records the same audio data content as the audio stream #0. Thiseliminates the need for switching audio streams at the boundaries inpartial dubbings, enabling uninterrupted reproduction at the boundaries.

FIG. 8 shows a data format of the video pack. FIGS. 9-11 show dataformats of audio packs.

In the DVD-RAM, each pack includes one packet. The pack is composed of apack header and a packet. The pack has a fixed size of 2 KB, which isthe same as the sector size in the DVD-RAM. The pack header includes apack start code, a System Clock Reference (SCR), and other data. The SCRis a kind of a time stamp and indicates a time at which the currentpack: passes through a demultiplexor of the reproducing apparatus. Here,the packs read from the DVD-RAM by the reproducing apparatus areseparated into video and audio packs by the demultiplexor. The videodata or audio data of each pack is stored in the video buffer or audiobuffer, and is decompressed (extended) by the video decoder or the audiodecoder.

Each packet includes a packet header and a payload field. The packetheader includes a packet start code, a stream ID, a DTS, a PTS, andother data.

The stream ID is an identifier indicating an elementary stream whichincludes the current pack.

The DTS (Decode Time Stamp) is a kind of time stamp and indicates a timeat which video picture data or audio frame data is transferred from thevideo buffer or audio buffer to a video decoder or an audio decoder. TheDTS is not attached to (omitted in) audio streams since audio streamsare decoded and presented at the same time.

The PTS (Presentation Time Stamp) is a kind of a time stamp andindicates a time at which decoded video data or decoded audio data isdisplayed/output.

In the present embodiment, the stream ID of the video stream is “11100000” as shown in FIG. 8. The stream ID of the audio stream encoded withthe MEPG audio is “1100 0000” (in case of the audio stream #0) or “11000001” (in case of the audio stream #1), as shown in FIG. 9. As shown inFIGS. 10 and 11, the stream ID of the audio streams encoded with theAC-3 or the linear PCM is “1011 1101” which is equivalent to the privatestream 1 defined in the MPEG2. Furthermore, either of the AC-3 and thelinear PCM, and, either of the audio stream #0 and the audio stream #1are identified by the sub-stream ID included in the packet payload.

The audio packs by the AC-3 or the linear PCM include a sub-stream IDfollowing the packet header. As shown in FIG. 10, the sub-stream ID ofthe audio stream encoded with the AC-3 is “1000 0000” (in case of theaudio stream #0) or “1000 0001” (in case of the audio stream #1). Asshown in FIG. 11, the sub-stream ID of the audio stream encoded with thelinear PCM is “1010 0000” (in case of the audio stream #0) or “10100001” (in case of the audio stream #1).

As described above, an elementary stream in which the current pack isincluded is identified by the stream ID and the sub-stream ID.

<1-2-2 AV Data Management File>

FIG. 12 hierarchically shows the data structure of the AV datamanagement file.

As shown in the first layer in the drawing, the AV data management fileincludes a VOB Information (VOBI) table and a PGC Information (PGCI)table.

<1-2-2-1 VOBI Table>

The VOBI table will be explained first.

As shown in the second layer in FIG. 12, the VOBI table includesinformation entitled “Number of VOBs,” “VOBI#1,” . . . “VOBI#N.” The“Number of VOBs” indicates the number of VOBs recorded on the DVD-RAMdisc (in the present example, the number is N). The “VOBI#1,” . . .“VOBI#N” are information of respective VOBs recorded on the DVD-RAMdisc.

As shown in the third layer in FIG. 12, each VOBI (“VOBI#1,” . . .“VOBI#N”) includes information entitled “AV File Name,” “VOB ID,” “VOBStart Address,” “VOB End Address,” “VOB Playback Time,” and “VOBAttribute.” The “VOB ID” is an identifier of the VOB. The “VOB StartAddress” and “VOB End Address” are represented by sector addresses.

As shown in the fourth layer in FIG. 12, each “VOB Attribute” includes“Video Attribute,” “Audio0 Attribute,” and “Audio1 Attribute.” The“Video Attribute” shows the resolution and aspect ratio (ratio of thevertical length to the horizontal length of the screen) of the videoimage in the video stream.

As shown in the fifth layer in FIG. 12, each of the “Audio0 Attribute”and “Audio1 Attribute” includes information entitled “Coding Mode,”“Application Flag,” “Quantization,” “Fs,” and “Number of Channels.” The“Coding Mode” shows an encoding mode which is any of the MPEG audio,AC-3, and linear PCM. The “Application Flag” shows the contents of theaudio stream. The “Quantization” includes information related to thequantization, such as a quantization coefficient. The “Fs” shows asampling frequency. The “Number of Channels” indicates the number ofchannels included in the audio stream.

The “Application Flag” of the “Audio1 Attribute” has at least two bits.The value of the “Application Flag” indicates any of “same audio data,”“nearly same audio data,” “dubbing audio data,” and “customized audiodata.”

The “same audio data” indicates that the audio data of the audio stream#1 is a copy of the audio data of the audio stream #0. That means theaudio stream #1 and the audio stream #0 are the same in every respect,that is, in each of the encoding mode, in: the bit rate, and in theaudio data for each pack. That is, all the packs included in the audiostream #1 in one VOB correspond to the packs included in the audiostream #0 on a one-to-one basis. Also, each pack in the audio stream #1has the same audio data as the audio data included in the correspondingpack in the audio stream #0.

The “nearly same audio data” indicates that the audio data of the audiostream #1 is not a copy of the audio data of the audio stream #0, butthe source is the same.

The “dubbing audio data” indicates that the audio data of the audiostream #1 is a dubbing. In this case, the value of the “ApplicationFlag” may indicate any of “same audio data,” “nearly same audio data,”and “customized audio data” before the dubbing is performed.

The “customized audio data” indicates that the audio data of the audiostream #1 is irrelevant to that of the audio stream #0. For example, theinformation indicates so when the audio data of the audio stream #1 issoundless data or audio data which is totally different from that of theaudio stream #0.

It should be noted here that in the present embodiment, the valuesprepared for the “Application Flag” of the “Audio0 Attribute” are thesame as those of the “Audio1 Attribute.” However,: the values of the“Application Flags” of the “Audio0 Attribute” and “Audio1 Attribute” maynot necessarily be the same. The values may always be set to “customizedaudio data” or may be different.

<1-2-2-2 PGCI Table>

Now, the PGCI table will be explained.

As shown in the second layer shown in FIG. 12, the PGCI table includesinformation entitled “Number of PGCs,” “PGCI#1,” . . . “PGCI#M.” The“Number of PGCS” indicates the number of PGCs recorded on the DVD-RAMdisc (in the present example, the number is M). Here, a“PGC” is alogically linked sequence of arbitrary sections in arbitrary VOBscontaining AV data, or is a playback route of the logically linkedsequence of AV data. Also, the “PGC information” is informationindicating the logical linkage relation (playback route) betweenarbitrary sections in arbitrary VOBs. When a VOB is newly recorded, aPGCI of a PGC which is a simple sequence sections in the VOB in theOrder is added to the PGCI table. The PGCI can be defined (edited) bythe user as a logically linked sequence of arbitrary sections inarbitrary VOBs containing AV data, or is a playback route of thelogically linked sequence of AV data.

As shown in the third layer in FIG. 12, each PGCI (“PGCI#1,” . . .“PGCI#M”) includes information entitled “Number of Cells” and “Cell 1,”. . . “Cell J.” Here, one “cell” is an arbitrary section in an arbitraryVOB which can be specified by the user. Now, suppose the “Number ofCells” in the PGCI#M is J, then the “PGCI#M” indicates a logicalsequence of sections containing AV data shown by “Cell 1,” . . . “CellJ.”

As shown in the fourth layer in FIG. 12, each of the “Cell 1,” . . .“Cell J” includes information entitled “VOB ID,” “Cell Start Time,”“Cell Playback Time,” “Cell Start Address,” “Cell End Address,” and“Audio Flag.”

The pair of the “Cell Start Time” C_ST) and “Cell Playback Time” C_PT)specifies a section (a cell) in the VOB specified by the “VOB ID.” Asshown in FIG. 13, the “Cell Start Time” C_ST) indicates the start of thesection using a PTS in the VOB. The end of the section is obtained byadding the C_PT to the C_ST.

The pair of the “Cell Start Address” and “Cell End Address” specifies asection (a cell) in the VOB specified by the “VOB ID.” As shown in FIG.13, the “Cell Start Address” C_SA) and “Cell End Address” C_EA) arewithin a range the “VOB Start Address” (V_SA) to the “VOB End Address”(V_EA). When a VOB is newly recorded, a PGCI of a PGC which is a cellincluding all sections of the VOB is added to the PGCI table.

The “Audio Flag” specifies an audio stream which should be reproducedwhen the cell is reproduced. That is, the “Audio Flag” indicates theaudio stream #0 when the flag has value “0,” and indicates the audiostream #1 when it has value “1.”

In the present embodiment, a cell is a section in a VOB specified byboth a pair of a C_ST and a C_PT and a pair of a C_SA and a C_EA, asshown in FIG. 13. However, a cell may be a section in a VOB specified byeither of the pair of a C_ST and a C_PT and the pair of a C_SA and aC_EA.

<1-2-2-3 Application Flag>

FIG. 14 shows a relationship between several pieces of informationindicated by respective values of the “Application Flag” of the “Audio1Attribute” in a VOBI shown in FIG. 12.

As shown in the solid lines in the drawing, a partial or a whole dubbingcan be performed on the audio stream #1 when the “Application Flag” is“same audio data” or “nearly same audio data.” After the dubbing iscomplete, the “Application Flag” changes to a value indicating “dubbingaudio data.” It is possible to regard “dubbing audio data” as“customized audio data.”

As shown in the dotted lines in FIG. 14, when the original applicationflag of the audio streams is “same audio data,” that is, the audio dataof the audio stream #0 is copied to the audio stream #1 when the audiostream #1 is first recorded onto the disc, the audio data of the audiostream #0 can be copied to the audio stream #1 even after the dubbing isperformed on the audio stream #1. After this is done, the applicationflag of the audio stream #1 indicates “same audio data” again.

It is possible to perform a whole dubbing on the audio stream #1 even ifthe application flag indicates “customized audio data.” After thedubbing is performed, the application flag indicates “dubbing audiodata.”

<2 Optical Disc Recording/Reproducing Apparatus>

The optical disc recording/reproducing apparatus in the presentembodiment is described below with reference to the drawings.

<2-1 System Using Optical Disc Recording/Reproducing Apparatus>

FIG. 15 shows the construction of an example system using the opticaldisc recording/reproducing apparatus of the present embodiment.

The system includes an optical disc recording/reproducing apparatus 10(hereinafter DVD recorder 10), a remote controller 6 for operating theDVD recorder 10, an antenna 11, and a display 12, where the antenna 11and display 12 are connected to the DVD recorder 10.

After the DVD-RAM disc, which is an optical disc and has been describedearlier, is loaded, the DVD recorder 10 compresses the video/audio datawhich is included in the analog broadcasting waves which is receivedthrough the antenna 11, records the compressed data as AV files into theDVD-RAM disc, expands the compressed video/audio data, and outputs theexpanded video/audio signals onto the display 12.

<2-2 Construction of DVD Recorder 10>

FIG. 16 is a block diagram showing the construction of the DVD recorder10. The DVD recorder 10 includes a control unit 1, an MPEG encoder 2, adisc access unit 3, an MPEG decoder 4, a video signal processing unit 5,a remote controller 6, a bus 7, a remote controller signal receivingunit 8, and a receiver 9.

The control unit 1 includes a CPU 1 a, a processor bus 1 b, a businterface 1 c, and a main memory 1 d. The control unit 1 executes aprogram stored in the main memory 1 d to control the entire DVD recorder10 in terms of recording, reproducing, editing, etc. Especially, afteran AV file (VOB) including AV data is recorded, the control unit 1generates VOB information and PGC information corresponding to therecorded VOB, and records or updates the AV data management file. Also,When the AV data is reproduced, the control unit 1 controls thereproduction of the section specified by information “Cell” included inthe PGC information in the AV data management file shown in FIG. 12.

The MPEG encoder 2 compresses the video/audio data which is included inthe analog broadcasting waves received by the receiver 9 through theantenna 11 and generates MPEG streams.

The disc access unit 3, having track buffers 3 a, performs the followingunder the control of the control unit 1: records the MPEG streamreceived from the MPEG encoder 2 into the DVD-RAM disc via one trackbuffer 3 a, reads out the MPEG stream from the DVD-RAM disc, and outputsthe read MPEG stream to the MPEG decoder 4 via one track buffer 3 a.During the dubbing process, the disc access unit 3 performs therecording and reproducing in parallel using a plurality of track buffers3 a.

The MPEG decoder 4 expands the compressed MPEG stream which is read outby the disc access unit 3, and outputs the expanded video data and audiosignals.

The video signal processing unit 5 converts the video data output fromthe MPEG decoder 4 into video signals for the display 12.

The remote controller signal receiving unit 8 receives remote controllersignals from the remote controller 6 shown in FIG. 17 and informs thecontrol unit 1 of which operation the user has instructed.

The DVD recorder 10 is, as shown in FIG. 15, constructed based on thepremise that it is used as a replacement for a VTR used at home. Notlimited to the construction, when the DVD-RAM disc is to be used as arecording medium for computers, the following constructions arepossible. That is to say, the disc access unit 3 is connected, as aDVD-RAM drive apparatus, to a computer bus via an IF called SCSI or IDE.Also, the components other than the disc access unit 3 shown in FIG. 3are achieved or operated when the OS and the application program areexecuted on the computer hardware.

Also, the DVD recorder 10 may be achieved as a camcorder (a recordercomprising a camera). In this case, the DVD recorder 10 includes acamera and a microphone instead of the receiver 9.

<2-2-1 MPEG Decoder 4>

FIG. 18 is a block diagram showing the construction of the MPEG decoder4 shown in FIG. 16. As shown in FIG. 18, the MPEG decoder 4 includes ademultiplexor 4 a for dividing MPEG streams into video streams and audiostreams, a video buffer 4 b for temporarily storing the divided videostreams, a video decoder 4 c for decoding the video streams stored inthe video buffer 4 b, an audio buffer 4 d for temporarily storing thedivided audio streams, an audio decoder 4 e for decoding the audiostreams stored in the audio buffer 4 d, and an STC (System Time Clock)unit 4 f for generating an STC which shows a reference time used in theMPEG decoder 4.

The demultiplexor 4 a divides an MPEG stream into a video stream and anaudio stream. The demultiplexor 4 a outputs the divided video stream tothe video buffer 4 b, and the divided audio stream to the audio buffer 4d. In doing so, the demultiplexor 4 a selects either of the audio stream#0 and the audio stream #1 as the divided audio stream in accordancewith a specification by the control unit 1 of an audio stream to bereproduced. The other one of the audio streams, not specified by thecontrol unit 1, is discarded.

The above process will be described more specifically. The demultiplexor4 a analyzes the pack header and the packet header of each pack includedin the input MPEG stream. The demultiplexor 4 a then refers to thestream ID and the sub-stream ID to identify the stream of each packwhich is any of the video stream, the audio stream #0, or the audiostream #1 for dubbing.

The demultiplexor 4 a discards packs when it finds the packs belong toan audio stream which is not specified by the control unit 1 as an audiostream to be reproduced.

When finding a pack which belongs to an audio stream specified by thecontrol unit 1, the demultiplexor 4 a outputs the audio data stored inthe payload field of the packet of the pack to the audio buffer 4 e withthe timing when the STC matches the SCR of the pack. At the same time,the demultiplexor 4 a outputs the PTS attached to the packet to theaudio decoder 4 e.

When finding a pack which belongs to the video stream, the demultiplexor4 a outputs the video data stored in the payload field of the packet ofthe pack to the video buffer 4 b with the timing when the STC matchesthe SCR of the pack. At the same time, the demultiplexor 4 a outputs theDTS and PTS assigned to the packet to the video decoder.

The data stored in the payload field of each pack is input to the videobuffer 4 b or the audio buffer 4 d at the time indicated by the SCR. Thedata stored in the video buffer 4 b or the audio buffer 4 d is fetchedfrom the buffer at the time indicated by the DTS.

<2-2-2 MPEG Encoder 2>

FIG. 19 is a block diagram showing the construction of the MPEG encoder2 shown in FIG. 16. As shown in FIG. 19, the MPEG encoder 2 includes avideo encoder 2 a, a video buffer 2 b, an audio encoder 2 c, an audiobuffer 2 d, a system encoder 2 e, an STC (System Time Clock) unit 2 f,an encoder control unit 2 g, and a dubbing unit 2 h.

The video encoder 2 a compresses the video signals received via thereceiver 9 and generates a video stream.

The video buffer 2 b temporarily stores the video stream output from thevideo encoder 2 a.

The audio encoder 2 c compresses the audio signals received via thereceiver 9 and generates an audio stream, during the recording process.The audio encoder 2 c compresses another audio source to generate anaudio stream, during the dubbing process. The other audio source is, forexample, an audio signal input through a microphone, or an audio signalwhich is a mixture of an audio signal input through a microphone and adecoded audio stream #0.

The audio buffer 2 d temporarily stores the audio stream output from theaudio encoder.

The system encoder 2 e, including an A1_pack buffer 2 e 1:

(a) generates packs of the video stream and the audio stream #0,

(b) generates audio packs of the audio stream #1 for dubbing, and

(c) performs multiplexing.

In the above (a) process, the system encoder 2 e fetches the videostream and the audio stream #0 respectively from the video buffer 2 band the audio buffer 2 d and sequentially generates video packs(V_PACKs) and audio packs (A0_PACKs). In the above (b) process, thesystem encoder 2 e generates audio packs (A1_PACKs) of the audio stream#1. In this process, the system encoder 2 e generates A1_PACKs bycopying the A0_PACKs of the audio stream #0 into the A1_pack buffer 2 e1, and rewriting a part of the pack header and the packet header. In themultiplexing in the above (c) process, the system encoder 2 esequentially outputs theV_(—PACK, A0_PACK, and A1_PACK one by one in the order indicated by the SCR. By repeating this, the system encoder 2)e outputs these packs as VOB to the disc access unit 3.

FIG. 25 shows the VOBs output from the system encoder 2 e. In thedrawing, “V” represents a video pack (V_PACK), “A#0” an audio pack ofthe audio stream #0 (A0_PACK), “A#1” an audio pack of the audio stream#1 (A1_PACK). Each pair of the A1_PACK and the A0_PACK corresponding toeach other have the same audio data, but has different stream IDs (orsub-stream IDs) and different SCRs. The SCR of the A1_PACK of a pair isequal to the SCR of the A0_PACK of the pair plus a predetermined valueα, so that they are multiplexed to be cated at adjacent or near placesin the VOB.

The STC unit 2 f generates an STC which shows a reference time used inthe encoder 2.

The dubbing unit 2 h, after a VOB read from the DVD-RAM disc is inputfrom the disc access unit 3 during the dubbing process, replaces theaudio data stored in the payload field of the A1_PACKs in the VOB withnew audio data fetched from the audio buffer 2 d, then outputs the VOBto the disc access unit 3 as a VOB after dubbing. FIG. 20 shows theoperation executed during the dubbing process. The drawing shows thatthe VOB is the same before and after the dubbing except that theA1_PACKs change to A1′_PACKs. That is, while the VOB read from theDVD-RAM disc is reproduced by the MPEG decoder 4, the dubbing unit 2 hsequentially stores the packs of the VOB before dubbing into the buffer2 h 1 then replaces the audio data of only the A1_PACKs among the storedpacks with other data.

The disc access unit 3, having track buffers 3 a, performs the followingunder the control of the control unit 1: records the MPEG streamreceived from the MPEG encoder 2 into the DVD-RAM disc via one trackbuffer 3 a, reads out the MPEG stream from the DVD-RAM disc, and outputsthe read MPEG stream to the MPEG decoder 4 via one track buffer 3 a.During the dubbing process, the disc access unit 3 performs therecording and reproducing in parallel using a plurality of track buffers3 a.

<2-2-3 Disc Access Unit 3>

FIG. 21 shows the construction of the disc access unit 3 shown in FIG.16. The disc access unit 3 includes track:buffers 3 a 1 to 3 a 4, anoptical pickup 3 b, an ECC (Error Correcting Code) processing unit 3 c,and switches 3 d and 3 e.

The track buffers 3 a 1 and 3 a 3 are used for reading data from thedisc and the track buffers 3 a 2 and 3 a 4 are used for writing onto thedisc.

The ECC processing unit 3 c performs the ECC process on the data readthrough the optical pickup 3 b in units of 16 sectors (in an ECC blockunit) when data on the disc is reproduced. The ECC processing unit 3 cperforms the ECC process on the data input though the switch 3 d in anECC block unit when data is written onto the disc.

The switch 3 d connects the ECC processing unit 3 c to the track buffer3 a 1 or 3 a 3 so that the read data is stored in the buffer when dataon the disc is reproduced, connects the ECC processing unit 3 c to thetrack buffer 3 a 2 or 3 a 4 when data is written onto the disc, andconnects the ECC processing unit 3 c to any of the track buffers 3 a 1to 3 a 4 in sequence so that the reproducing and writing are performedin real time when the dubbing process is executed.

The switch 3 e connects the track buffer 3 a 1 or 3 a 3 to the MPEGdecoder 4 when data on the disc is reproduced, connects the track buffer3 a 2 or 3 a 4 to the MPEG encoder 2 when data is written onto the disc.When the dubbing process is executed, the switch 3 e connectsalternately the track buffer 3 a 1 and 3 a 3 to the MPEG decoder 4 andconnects alternately the track buffer 3 a 2 and 3 a 4 to the MPEGencoder 2.

Since the switches 3 d and 3 e operate as described above, the readingfrom the optical disc or the writing onto the disc can be performed inparallel with the rewriting of the audio stream #1 performed by the MPEGencoder 2. For example, the reading data from the optical disc andstoring the read data into the track buffer 3 a 3 can be performed inparallel with the updating of the audio stream #1 stored in the trackbuffer 3 a 1 and storing the updated audio stream into the track buffer3 a 2. This makes it possible to perform the dubbing in real time whilethe disc is reproduced.

<2-3 Writing>

When the user presses RECORD key on the remote controller 6, the controlunit 1 is notified of it via the remote controller signal receiving unit8 and the bus 7 shown in FIG. 16.

After receiving the above notification, the control unit 1 instructs theMPEG encoder 2 to compress the video/audio signal included in the analogbroadcasting wave the receiver 9 has received. The control unit 1 theninstructs the disc access unit 3 to write the VOBs obtained by thecompression onto the optical disc.

With the above control, the MPEG encoder 2 shown in FIG. 19 outputs thevideo stream compressed by the video encoder 2 a to the video buffer 2 band outputs the audio stream #0 compressed by the audio encoder 2 c tothe audio buffer 2 d, in sequence.

The system encoder 2 e generates the audio stream #1 while fetching thevideo stream and the audio stream #0 respectively from the video buffer2 b and the audio buffer 2 d, and multiplexes the three streams intoVOBs and outputs the VOBs to the disc access unit 3 via the bus 7.

More specifically, the system encoder 2 e: (a) generates packs of thevideo stream and the audio stream #0, (b) generates audio packs of theaudio stream #1, and (c) performs multiplexing, as described earlier.

<2-3-1 Generating Video Packs>

FIG. 22 is a flowchart showing the process of generating packs of thevideo stream and the audio streams #0 and #1, the process beingperformed by the system encoder 2 e.

The system encoder 2 e, the instant when the video encoder 2 a startsencoding, performs simulations of the amount of the video data and audiodata respectively occupying the video decoder buffer (equivalent to thevideo buffer 4 b shown in FIG. 18) of a reproducing apparatus and theaudio decoder buffer (equivalent to the audio buffer 4 d shown in FIG.18) of the reproducing apparatus (step 221). The data stored in thepayload field of each video pack is input to the video decoder buffer ofthe reproducing apparatus at the time indicated by the SCR. The data isfetched from the video decoder buffer at the time indicated by the DTS.The capacity of the video decoder buffer has a limit (224 KB accordingto the standard). Therefore, when the SCR of the pack is definedregardless of the video decoder buffer capacity, the buffer mayoverflow. The simulation is performed in the step 221 to check thechange in the amount of the video data and audio data respectivelyoccupying the video decoder buffer (equivalent to the video buffer 4 bshown in FIG. 18) of a reproducing apparatus and the audio decoderbuffer (equivalent to the audio buffer 4 d shown in FIG. 18) of thereproducing apparatus, in accordance with changes in the SCR and DTS ofthe pack.

FIG. 26 shows the simulation of the video decoder buffer. In thedrawing, the horizontal axis represents time, and the vertical axis theamount of video data occupying the video decoder buffer, T0 the timewhen the video decoder buffer starts receiving data, and Vin (theinclination of the graph) the data input bit rate. Also, T2 and T4-T6each represent the times when data is fetched from the video decoderbuffer. The drawing is written based on the presumption that datatransfer from the video decoder buffer to the decoder is performedinstantaneously.

The time T1 indicates the time when a certain amount of data fetchedfrom the buffer at time T4 started being input to the buffer. Similarly,time T3 indicates the time when a certain amount of data fetched fromthe buffer at time T5 started being input to the buffer. The time periodbetween the input and output of a certain amount of data to/from thevideo decoder buffer is called VBV delay.

The simulation of occupation of the audio decoder buffer by audio datais similar to the simulation of the video decoder buffer shown in FIG.26. However, the audio stream has far smaller amount of data (bit rate)than the video stream. Also, the capacity of the audio decoder buffer (4KB according to the standard) is smaller than that of the video decoderbuffer.

The system encoder 2 e determines a pack of which of video data andaudio data should be generated, in accordance with the amount of datastored in the video buffer 2 b and the audio buffer 2 d (step 222).

When determining as video data in step 222, the system encoder 2 efetches a predetermined amount of video data (equivalent to the size ofthe payload field of the video packet) from the video buffer 2 b (step223), and attaches the packet header and the pack header to the fetchedvideo data (step 224).

When determining as audio data in step 222, the system encoder 2 efetches a predetermined amount of audio data (equivalent to the size ofthe payload field of the audio packet) from the audio buffer 2 d (step225), and attaches the packet header and the pack header to the fetchedaudio data (step 226). A pack for the audio stream #1 for dubbing isthen generated from the pack for the audio stream #0. That is, the packfor the audio stream #1 is generated by copying the pack for the audiostream #0 (step 227).

The system encoder 2 e stores the generated pack in a video or audiopack buffer (not illustrated) in itself (step 229). When an endinstruction is not detected, control returns to the step 221 (step 230).The generated video/audio packs are stored in the video/audio packbuffers until they are fetched in the multiplexing process.

By repeating the above steps 221 to 230, the system encoder 2 esequentially generates the video/audio packs for the video stream, theaudio stream #0, and the audio stream #1 respectively stored in thevideo buffer 2 b and audio buffer 2 d.

<2-3-2 Generating Packs of Audio Stream #1>

FIG. 23 is a flowchart showing the process of generating audio packs ofthe audio stream #1 for dubbing. That is, the drawing shows a detailedprocess of step 227 shown in FIG. 22.

When a newly created A0 PACK is stored in a pack buffer (notillustrated) (step 231), the system encoder 2 e copies the A0_PACK tothe A1_pack buffer 2 e 1 (step 232).

The system encoder 2 e then changes the audio stream number specified bythe stream ID or sub-stream ID in the A0_PACK stored in the A1_packbuffer 2 e 1 from #0 to #1, and changes the value of a copy/originalflag from “0” to “1” (step 234). The system encoder 2 e changes thevalue of the SCR so that the A1_PACK is located immediately after ornear the A0_PACK in a VOB (step 235).

Audio packs of the audio stream #1 are generated as described above. Thegenerated A1_PACKs are stored in the A1_pack buffer 2 e 1 until they arefetched in the multiplexing process.

The SCR value is changed as described above due to the following reason.If there are two packs having the same SCR, the reproducing apparatusoutputs the two packs at the same time to the demultiplexor locatedbefore the audio decoder buffer. This may cause an abnormal operation ofthe demultiplexor.

<2-3-3 Multiplexing>

FIG. 24 is a flowchart of the multiplexing process in which the systemencoder 2 e multiplexes the video stream and the audio streams #0 and #1in units of packs.

The system encoder 2 e performs the multiplexing process as follows, inparallel with the generation of the video pack, A0_PACK, and A1_PACKshown in FIGS. 22 and 23.

The system encoder 2 e judges whether one or more packs are stored inany of the video pack buffer, audio pack buffer, and the A1_pack buffer(step 241). When having judged that one or more packs are stored, thesystem encoder 2 e reads the SCRs of the packs and detects a pack havingthe SCR with the earliest time (step 242). The system encoder 2 eoutputs the detected pack and deletes the pack from the buffer (step243). By repeating these steps, the video packs, A0_packs, and A1_packsare multiplexed into one VOB in the order of time indicated by the SCRas a sequence of packs.

After one VOB is written onto the disc, the control unit 1 newlygenerates the VOB information and the PGC information shown in FIG. 12and adds the generated information to the AV data management file. Inthe newly generated VOB information, the application flag of the audiostream #1 for dubbing is set to “same audio data.” The application flagof the audio stream #0 is set to the same value as the audio stream #1.The newly generated PGC information includes a cell having a playbacksection ranging from the start to the end of the newly written VOB. Theaudio flag included in the cell specifies “audio stream #0.”

<2-4 Dubbing>

When the user presses DUBBING key on the remote controller 6 afterspecifying PGC, the control unit 1 is notified of it via the remotecontroller signal receiving unit 8 and the bus 7 shown in FIG. 16.

After receiving the above notification, the control unit 1 reads the PGCinformation and the VOB information from the AV data management file,and determines a VOB to be dubbed.

The, control unit 1 controls the disc access unit 3 and the MPEG decoder4 to read the determined VOB from the optical disc and reproduce it. Inparallel with this, the control unit 1 controls the MPEG encoder 2 andthe disc access unit 3 to modify only the audio stream #1 in the VOBread by the disc access unit 3 and to write the modified VOB onto theoptical disc.

FIG. 27 shows the dubbing process with the timing when the disc accessunit 3 performs reading/writing, and with the timing when the MPEGencoder 2 rewrites the audio stream #1. FIG. 29 shows the control of theswitches 3 d and 3 e shown in FIG. 21 performed by the control unit 1with the timing shown in FIG. 27.

In FIG. 27, TB1 to TB4 respectively represent the track buffers 3 a 1 to3 a 4 in the disc access unit 3 shown in FIG. 21. The horizontal axisrepresents time, and the vertical axis the amount of data occupying eachtrack buffer.

T1, T2, T4, and T6 respectively represent the time periods during whichVOBs before dubbing are read from the optical disc and stored into TB1,TB3, TB1, and TB3 via the switch 3 d. T3, T5, T7, and T8 respectivelyrepresent the time periods during which VOBs after dubbing are fetchedfrom TB2, TB4, TB2, and TB4 and written onto the optical disc via theswitch 3 d.

FIG. 28 shows a VOB which is read and written during the time periodsshown in FIG. 27. For example, a section (A) of the VOB before dubbingis read during T1 and the section (A) after dubbing is written onto thedisc during T3.

In FIG. 27, Ta and Tc respectively represent the time periods duringwhich VOBs stored in TB1 are dubbed and stored into TB2. During thesetime periods, the dubbing unit 2 h of the MPEG encoder 2 replaces theaudio data stored in the payload field of each pack of the audio stream#1 with new audio data.

Tb and Td respectively represent the time periods during which VOBsstored in TB3 are dubbed and stored into TB4.

As shown in FIG. 27, there is no gap between the time periods Ta, Tb,Tc, and Td. That is, these time periods are successive. This is achievedby the control performed by the control unit 1 in which the control unit1 alternately connects two pairs of TBs (a pair of TB1 and TB2 and apair of TB3 and TB4) to the MPEG encoder 2 for each Ta, Tb, Tc, and Tdso that the dubbing is performed, and at the same time, and uses theother pair of TBs (the pair which is not used in the dubbing) toread/write. data from/onto the optical disc. This enables the dubbingunit 2 h of the MPEG encoder 2 to perform the dubbing consecutively inreal time.

It is also possible to perform a partial dubbing by instructing theON/OFF of the dubbing operation using the remote controller during thedubbing process. This is explained in detail. When receiving aninstruction to execute the dubbing (ON) from the remote controllersignal receiving unit 8 via the bus 7, the control unit 1 instructs thedubbing unit 2 h of the MPEG encoder 2 to replace the audio data storedin the payload field of the current audio pack of the audio stream #1with new audio data; when receiving an instruction to pause the dubbing(OFF), the control unit 1 instructs the dubbing unit 2 h to pausereplacing data.

It is also possible to return the dubbed audio stream #1 to the statebefore dubbing. To achieve this, the dubbing unit 2 h writes the audiodata stored in the payload field of each pack of the audio stream #0over that of the audio stream #1.

Each time a VOB included in a PGC is dubbed, the:control unit 1 updatesthe application flag of the audio streams #1 of the corresponding VOBinformation to “dubbing audio data,” without updating the applicationflag of the audio streams #0. The reason for not changing theapplication flag of the audio streams #0 is as follows. Even after theaudio stream #1 is dubbed, it is possible to return the dubbed audiostream #1 to the state before dubbing without encoding when theapplication flag of the audio streams #0 is “same audio data,” orwithout re-encoding the decoded audio signal when the application flagof the audio streams #0 is “nearly same audio data.” This arrangement isuseful for the user. For example, when the user has failed to performdubbing, the user can judge whether the dubbed audio stream #1 can bereturned to the state before dubbing by referring to the applicationflag of the audio stream #0, and if it can, the user can perform thedubbing again after returning the dubbed audio stream #1 to the statebefore dubbing.

<2-5 Reproduction Process>

When the user presses PLAY key on the remote controller 6, the controlunit 1 is notified of it via the remote controller signal receiving unit8 and the bus 7 shown in FIG. 16. After receiving this notification, thecontrol unit 1 determines a VOB by reading out the PGC information andthe VOB information from the AV data management file. In doing so, thecontrol unit 1 also determines which of the audio streams #0 and #1should be reproduced by referring to the audio flag included in the PGCinformation, and notifies the MPEG decoder 4 of the determinationresult.

The control unit 1 controls the disc access unit 3 and the MPEG decoder.4 to read the determined VOB from the optical disc and reproduce it.

With the above operation, the PGC specified by the user is reproduced.

When the user instructs the change of the audio streams operating theremote controller 6 and when the application flag of the audio stream #1indicates “same audio data” or “nearly same audio data,” the controlunit 1 does not change the audio streams and instructs the video signalprocessing unit 5 to temporarily add guidance information to the videosignal to show the user that the change of the audio stream is notavailable. This is because the user instructs the change expecting adifferent audio, while the same audio will be reproduced with theapplication flag indicating “same audio data” or “nearly same audiodata” even if the audio stream is switched from #0 to #1, and in thiscase the user may misunderstand the operation to think that the DVDrecorder has broken down and failed to change the audio streams.

When the user instructs the change of the audio streams operating theremote controller 6 and when the application flag of the audio stream #1indicates “dubbing audio data” or “customized audio data,” the controlunit 1 instructs the MPEG decoder 4 to change the audio stream from #0to #1.

As apparent from the above description, the VOBs recorded onto theoptical disc DVD-RAM of the present embodiment each have a predeterminedamount of space that can store data for dubbing. This enables the audiodata to be dubbed in VOBs without re-encoding or re-locating the VOBs.

In the present embodiment, the dubbing can be performed withoutdifficulty only by replacing audio data in the packs with other datasince the above predetermined amount of space is achieved as an audiostream.

In the present embodiment, the recorder can perform the dubbing withoutdifficulty since the same audio data as the audio stream #0 which isoriginal is recorded in the audio stream #1 for dubbing.

The recorder can generate the audio stream for dubbing withoutdifficulty when the same encoding mode and the same bit rate areassigned to both the audio streams #0 and #1. In this case, the recorderachieves this only by copying packs of the audio stream #0 and changinga part of the packs (the SCRs, and stream IDs or the sub-stream IDs)when recording the VOBs onto the disc.

The optical disc of the present invention can be achieved as an opticaldisc for Karaoke in which the audio stream #0 as original audio data andthe audio stream #1 for dubbing are multiplexed into the VOBs. With thisconstruction, the sound input through a microphone can be mixed into theoriginal audio data recorded in the audio stream for dubbing. Also, apartial dubbing or a whole dubbing can be repeated.

In the present embodiment, each VOB includes two audio streams. However,only an audio stream for dubbing may be included in each VOB when thereis no original audio stream. In such a case, soundless data may berecorded into the audio stream for dubbing, for example.

In the present embodiment, the audio stream #1 for dubbing is generatedby copying the audio stream #0. However, the audio stream #1 for dubbingmay be generated as a different stream (e.g., a stream other than theaudio stream, or an audio stream storing soundless data).

The audio stream #1 may be recorded with a different encoding mode or adifferent sampling frequency from the audio stream #0 in the presentembodiment. This is achieved by allowing the MPEG encoder to include twopairs of an audio encoder and an audio buffer. FIG. 30 shows theconstruction of the MPEG encoder. Compared to the construction shown inFIG. 19, the present construction additionally includes an audio encoder2 c 1 and an audio buffer 2 d 1. With the present construction, it ispossible to record the audio stream #1 with the application flagindicating “nearly same audio data.”

It is also possible to perform dubbing by replacing the audio data inthe audio stream #0 in units of packs. In this case, the “Audio0Attribute” is used to manage the state of the audio stream #0 regardingwhether the stream has been dubbed or not.

In the present embodiment, the value of the copy/original flag in theA1_PACK may be changed to “0” (original) after the pack is dubbed. Also,the value of the copy/original flag in the A1_PACK may indicatedifferently. For example, the flag may be set to indicate “original”when it is first recorded onto the disc.

Furthermore, the reproduction time periods of the audio stream #0 and #1may not completely match. For example, the audio stream #1 may begenerated by copying the audio stream #0 by excluding a part of thestream #0 which corresponds to a reproduction time period not expectedto be dubbed.

<Second Embodiment>

<1 Optical Disc>

The optical disc of Second Embodiment differs from that of FirstEmbodiment in that a sub-picture stream for dubbing is multiplexed intoVOBs. Here, the sub-picture (hereinafter referred to as SP) is a stillpicture superimposed on the video picture as a subtitle, textualinformation or the like.

The following description focuses on characteristics of the presentembodiment.

FIG. 31 shows a structure of the VOB in the present embodiment in whichelementary streams (video streams, audio streams, and SP streams) aremultiplexed.

In the drawing, the SP stream 76 is still picture data (e.g., a codesequence generated by compressing a bit map image with the run-lengthencoding method) which includes a plurality of pieces of still picturedata respectively corresponding to a plurality of VOBUs in the VOB.However, since the SP stream 76 is used for dubbing, the SP stream 76 isonly required to have a predetermined size (e.g., a size correspondingto one half of the display screen to be displayed at the bottom of thescreen) and may be composed of invalid image data when the SP stream 76is first recorded onto the disc. As shown in the pack sequence in FIG.31, the SP stream 76 is multiplexed into the VOB as packs together withthe video stream and the audio streams #0 and #1.

SP packs in a VOBU are effective during the reproduction period of theVOBU. That is, image data of at least one still picture is distributedover one VOBU as SP packs and is superimposed on the video image duringthe reproduction period of the VOBU.

FIG. 32 shows a data format of the SP pack. In the drawing, thesub-stream ID “0010 0000” indicates the SP pack. The other elements ofthe data format is the same as the data format shown in FIGS. 10 and 11.

FIG. 33 hierarchically shows the data structure of the AV datamanagement file. The present data structure is different from that shownin FIG. 12 in that it additionally has an SP attribute.

As shown in the fourth and fifth layers, the SP attribute includes anapplication flag. The present application flag may be different fromthat in the First Embodiment. That is, the value of the “ApplicationFlag” indicates either “dubbed” or “not dubbed.” However, when only oneSP stream is multiplexed into a VOB, the application flag is set to“customized SP data” when the SP stream is first recorded onto the disc,and the application flag is set to “dubbing SP data” when the dubbing isperformed on the SP stream.

<2 Optical Disc Recording/Reproducing Apparatus>

The optical disc recording/reproducing apparatus (hereinafter referredto as recorder) in the present embodiment differs from that in the FirstEmbodiment in that it includes MPEG encoder 12 and MPEG decoder 14instead of MPEG encoder 2 and MPEG decoder 4. The following descriptionfocuses on characteristics of the present embodiment.

FIG. 34 is a block diagram showing the construction of the MPEG encoder12. Compared to the construction of the MPEG encoder 2 shown in FIG. 19,the present construction includes an SP encoder 2 i and an SP buffer 2j, and includes a system encoder 2 k and a dubbing unit 2 m instead ofthe system encoder 2 e and the dubbing unit 2 h.

The SP encoder 2 i generates the SP stream by encoding SP data for eachVOBU with the run-length encoding method.

The SP buffer 2 j temporarily stores the contents of the SP streamgenerated by the SP encoder 2 i in sequence.

The system encoder 2 k has a function to generate SP packs of the SPstream for dubbing when the VOB is recorded onto the disc, as well asthe functions of the system encoder 2 e. That is, the system encoder 2 kgenerates SP packs corresponding to a predetermined size of stillpicture data for each VOBU. In doing so, invalid data may be included inthe SP packs. The generated SP packs are multiplexed into the VOBtogether with the video packs and the audio packs (A0_PCKs and A1_PCKs).Alternatively, the dontents of the SP stream stored in the SP buffer maybe converted to packs and multiplexed into the VOB in sequence.

The dubbing unit 2 m has, as well as the functions of the dubbing unit 2h, a function to replace, for each VOBU, the data stored in the payloadfield of the SP PACKs with the contents of the SP stream stored in theSP buffer. For this purpose, the dubbing unit 2 m has a pack buffer 2 m1 for storing the SP packs of the VOB used for the above replacement.

FIG. 35 is a block diagram showing the construction of the MPEG decoder14. Compared to the construction of the MPEG decoder 4 shown in FIG. 18,the present construction includes an SP buffer 4 g, an SP decoder 4 h,and a combining unit 4 i.

The SP buffer 4 g temporarily stores the SP packs having been separatedfrom the VOB by the demultiplexor 4 a.

The SP decoder 4 h decodes the data (having been encoded with therun-length encoding method) in the SP packs transferred from the SPbuffer 4 g.

The combining unit 4 i combines the video data output from the videodecoder 4 c with the still picture data output from the SP decoder sothat the still pictures are superimposed on the video images.

As apparent from the above description, the VOBs recorded onto theoptical disc of the present embodiment each have a predetermined amountof space that can store sub-picture data for dubbing. This enables thesub-pictures to be dubbed in VOBs without re-encoding or re-locating theVOBs.

In the present embodiment, only one SP stream for dubbing is multiplexedinto each VOB. However, two SP streams may be multiplexed into each VOBas two audio streams are multiplexed in the First Embodiment.

In the present embodiment, three types of audio encoding modes: MPEGaudio, AC-3, and linear PCM are used. However, not limited to thesemodes, other encoding modes can be adopted.

In the present embodiment, it is described that one pack includes onepacket. However, one pack may include a plurality of packets.

In the present embodiment, DVD-RAM is used as a recording medium.However, not limited to this, other rewriteable media such as MO or HDDcan be used to obtain the same effects.

The present invention has been fully described by way, of examples withreference to the accompanying drawings, it is to be noted that variouschanges and modifications will be apparent to those skilled in the art.Therefore, unless such changes and modifications depart from the scopeof the present invention, they should be construed as being includedtherein.

What is claimed is:
 1. A recording apparatus for recording an inputvideo signal and an input audio signal onto an optical disc, comprising:a video stream generator operable to generate a video stream by encodingthe video signal; an audio stream generator operable to generate a firstaudio stream by encoding the audio signal, and to generate a secondaudio stream for dubbing based on the generated first audio stream; amultiplexer operable to multiplex the generated video stream, firstaudio stream, and second audio stream to generate a video object; arecording means for recording the video object onto the optical disc;and a controller operable to control the video stream generator, theaudio stream generator, the multiplexer and the recording means, areading means for reading the video object from the optical disc; and adecoder operable to decode the video stream and the first audio streamto obtain the video signal and the audio signal, wherein the audiostream generator generates the first audio stream includes a pluralityof packs having a fixed size, and generates the second audio streamhaving the same bit rate as the first audio stream and including thesame number of packs as the first audio stream, each pack having thesame size as the first audio stream, and the controller controls therecording means to rewrite a part or all of the second audio streamincluded in the video object recorded on the optical disc based on anaudio signal input for dubbing while controlling the decoder to decodethe video stream and the first audio stream.
 2. The recording apparatusof claim 1, wherein each of the first and second audio streams includesa plurality of reproduction sections respectively associated with timestamps which each specifies a presentation time of a corresponding oneof the reproduction sections, and the audio stream generator generatesthe second audio stream to have the time stamps to allow the secondaudio stream to be presented from the same start reproduction time tothe same end reproduction time as the first audio stream.
 3. A recordingmethod for recording an input video signal and an input audio signalonto an optical disc, comprising: generating a video stream by encodingthe video signal; generating a first audio stream by encoding the audiosignal to include a plurality of packs having a fixed size; generating asecond audio stream for dubbing based on the generated first audiostream to have the same bit rate as the first audio stream and toinclude the same number of packs as the first audio stream, each packhaving the same size as the first audio stream; multiplexing thegenerated video stream, first audio stream, and second audio stream togenerate a video object; recording the video object onto the opticaldisc; reading the video object from the optical disc; decoding the videostream and the first audio stream to obtain the video signal and theaudio signal; and dubbing a part or all of the second audio streamincluded in the video object recorded on the optical disc based on anaudio signal input for dubbing, wherein dubbing is performed while thevideo stream and the first audio stream are decoded.
 4. The recordingmethod of claim 3, wherein each of the first and second audio streamsincludes a plurality of reproduction sections respectively associatedwith time stamps which each specifies a presentation time of acorresponding reproduction section, and the second audio stream isgenerated to have the time stamps to allow the second audio stream to bepresented from the same start reproduction time to the same endreproduction time as the first audio stream.
 5. A computer-readablerecording medium recording a program that allows a computer to execute arecording method for recording an input video signal and an input audiosignal onto an optical disc, the recording method comprising: generatinga video stream by encoding the video signal; generating a first audiostream by encoding the audio signal to include a plurality of packshaving a fixed size; generating a second audio stream for dubbing basedon the generated first audio stream to have the same bit rate as thefirst audio stream and to include the same number of packs as the firstaudio stream, each pack having the same size as the first audio stream;multiplexing the generated video stream, first audio stream, and secondaudio stream to generate a video object; recording the video object ontothe optical disc; reading the video object from the optical disc;decoding the video stream and the first audio stream to obtain the videosignal and the audio signal; and dubbing a part or all of the secondaudio stream included in the video object recorded on the optical discbased on an audio signal input for dubbing, wherein dubbing is performedwhile the video stream and the first audio stream are decoded.
 6. Thecomputer-readable recording medium of claim 5, wherein each of the firstand second audio streams includes a plurality of reproduction sectionsrespectively associated with time stamps which each specifies apresentation time of a corresponding reproduction section, and thesecond audio stream is generated to have the time stamps to allow thesecond audio stream to be presented from the same start reproductiontime to the same end reproduction time as the first audio stream.